| Summary: | Temporal and spatial variation of body size within copepod species is well-known to be associated with variability of temperature and food supply. The study of patterns of growth, development and changes in body size of various species reared in the laboratory, allows an interpretation of the mechanisms regulating copepod size. Under satiating food, growth in body length was nearly linear and growth in body mass varied with species. Calanus finmarchicus with variable lipid contents showed exponential growth in total dry weight (TW) and lipid discounted dry weight (SW). In C.glacialis exponential growth was obscured by delayed development of late stages. Eurytemora herdmani with no visible lipids showed a clear exponential growth in TW. Temperature and food affected body length and body mass differently, thus altering body density. Food effect was more pronounced than that of temperature, and it was expressed in lipid content, influencing TW but not SW. It was hypothesized that food and temperature influence body size by altering timing of development and hence growth rates. Within treatments there was a weak correlation or lack of it between stage durations and body size, suggesting again that timing of development, but not size itself, regulate growth and development rates, which in turn determine size variations. Analysis of nuclear DNA content of 3 species subjected to food-temperature treatments suggested that genome size has a fundamental role in controlling development rates and indirectly body sizes. There were significant food-temperature effects on nuclear DNA, associated with effects on body size. Body size was negatively correlated to nuclear DNA contents in two of the three species. A negative correlation between nuclear DNA content and development rate in C.glacialis suggested that the role of genome size is more directly related to cell development rates rather than to cell size. Thesis (Ph.D.)--Dalhousie University (Canada), 1990.
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